1. Field of the Invention
This invention relates generally to the field of turbochargers having variable turbine inlet geometries. More particularly, the present invention provides a structural arrangement for variable inlet vane support independent of the turbine housing.
2. Description of the Related Art
In a turbocharger it is often desirable to control the flow of exhaust gas into the turbine to improve the efficiency or operational range. Various configurations of variable nozzles have been employed to control the exhaust gas flow. Multiple pivoting vanes annularly positioned around the turbine inlet and commonly controlled to alter the throat area of the passages between the vanes is an approach which has been successfully used in prior turbochargers. Various approaches to this method for implementing a variable nozzle are disclosed in U.S. Pat. No. 4,679,984 to Swihart et al. entitled “Actuation System for Variable Nozzle Turbine” and U.S. Pat. No. 4,804,316 to Fleury entitled “Suspension for the Pivoting Vane Actuation Mechanism of a Variable Nozzle Turbocharger” having a common assignee with the present application.
While multiple vane variable nozzle turbochargers have significantly increased the overall efficiency and capability of turbochargers, the complexity of support and actuation structures for the vanes have increased manufacturing costs and occasionally created maintenance issues. Additionally, connection of the vane support structure to the turbine housing limits flexibility in turbine housing design and structure. Turbine housings are a significant thermal load which can affect emissions systems performance in automotive applications. Further, integration of turbine housings into the exhaust manifold can provide a reduction in parts count and complexity for an automotive turbocharger installation. It is therefore desirable to provide variable nozzle structural support arrangements independent of the turbine housing to improve the actuation systems to increase reliability and reduce manufacturing costs for turbochargers employing them.